SearchServiceApplication searchServiceApp = srchApp.First();
searchSchema = new Schema(searchApplication);This does not seemed to be the best way to get to a service application and after some time of research I found out that you can also write it like this, which seems a better way to me:

searchApplication = (SearchServiceApplication)SPFarm.Local.Services.
GetValue().
Applications.GetValue(“Our other search service application”);
It took us several hours to find this out, but I hope that these snippets can save someone a few hours in the future.